Electrochemical cell having gas flow channels surrounded by solid electrolyte and interconnector

ABSTRACT

An electrochemical cell including at least one dense solid electrolyte body, at least two dense interconnectors for collecting current flowing the cell, cathodes and anodes, wherein the at least one dense solid electrolyte body and at least two dense interconnectors constitute a structural body, a plurality of first gas flow channels and a plurality of second gas flow channels both extend in a given direction, and are each defined and surrounded by a part of the at least one solid electrolyte body and a part of the at least two interconnectors, the anodes are formed on respective walls defined by a part of at least one solid electrolyte body and a part of at least two interconnectors and constituting the respective first gas flow channels, the cathodes are formed on respective walls defined by a part of at least one solid electrolyte body and a part of at least two interconnectors and constituting the respective second gas flow channels, every anode is opposed to an adjacent cathode or adjacent cathodes via a solid electrolyte body, and every cathode is opposed to an adjacent anode or adjacent anodes via a solid electrolyte body.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to electrochemical cells such as solidoxide fuel cells (SOFCs), steam electrolysis cells, oxygen pumps, andNOx decomposition cells. The invention also relates to a producingprocess for the production of such electrochemical cells, andelectrochemical devices using such electrochemical cells.

(2) Related Art Statement

The solid oxide fuel cells (SOFCs) are broadly classified into theso-called flat planar type and the so-called tubular type. Although itis said that the tubular type SOFC is most likely to be practicallyused, the flat planar type SOFC is more advantageous from the standpointof the output density per unit volume. However, in the flat planar typeSOFC, an electric power-generating stack is constructed by alternativelylaminating so-called separators and electric power-generating layers,but the SOFC thus produced has a difficult problem in sealing.

On the other hand, so-called integrated (monolithic) type SOFCsdifferent from the above type SOFCs are proposed. The above-mentionedtubular SOFC and the flat planar type SOFC are of a design in whichseparate unit cells are laminated successively one upon another. To thecontrary, the monolithic type SOFC was proposed by Argonne NationalLaboratory in the United States, is obtained by preliminarily preparinggreen sheets of respective components of the SOFC, forming a laminatethrough laminating the above green sheets of the components in a givenshape, and sintering the entire laminate. The monolithic type SOFCsinclude a parallel flow type (co-flow type) and an orthogonal flow type(cross flow type). It is expected that the monolithic type SOFC canrealize an extremely high output density of as high as around 8 kW/kg(“Fuel Cell Generation” published by CORONA PUBLISHING CO., LTD. in May20, 1994).

Among them, the parallel flow type SOFC is constructed such thatcorrugated three layers of a fuel electrode, a solid electrolyte and anair electrode are integrated, and the thus integrated corrugatedlaminate is sandwiched by flat planar interconnectors. The orthogonalflow type SOFC is constructed such that the flat planar electrodes andelectrolyte plate are laminated and sandwiched between corrugatedinterconnector. However, these fine constructions are so complicatedthat it is difficult to form a molded body by laminating respectivegreen sheets of the air electrode, the fuel electrode, the solidelectrolyte and the interconnector. In addition, since the airelectrode, the fuel electrode, the solid electrolyte and theinterconnector have utterly different porosities, characteristics, andoptimum sintering temperatures, it is extremely difficult to finish SOFCcomponents having their respective favorable characteristics bysimultaneous sintering. Consequently, although the monolithic type SOFChas been proposed well before, it has been considered difficult topractically use such a monolithic type SOFC, and it is a presentsituation that such monolithic SOFC cells are still in a trial stage.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide electrochemicalcells having a large electrode area per unit volume and a highefficiency. Further, it is another object of the present invention toprovide a new electrochemical cell structure which is structurallyrelatively simple, needs not special structurally sealing mechanism, andcan be produced by simultaneous sintering. It is a further object toprovide a process for producing such an electrochemical cell, and alsoto provide an electrochemical device using such an electrochemical cellor such electrochemical cells.

An electrochemical cell according to the present invention includes atleast one dense solid electrolyte body, at least two denseinterconnectors for collecting current flowing in the cell, cathodes andanodes, wherein said at least one dense solid electrolyte body and atleast two dense interconnectors constitute a structural body, aplurality of first gas flow channels and a plurality of second gas flowchannels both extend through the structural body in a given direction,and are each defined and surrounded by a part of said at least one solidelectrolyte body and a part of said at least two interconnectors, theanodes are formed on respective walls defined by said part of at leastone solid electrolyte body and said part of at least two interconnectorsand constituting the respective first gas flow channels, the cathodesare formed on respective walls defined by said part of at least onesolid electrolyte body and said part of at least two interconnectors andconstituting the respective second gas flow channels, every anode isopposed to an adjacent cathode or adjacent cathodes via a solidelectrolyte body, and every cathode is opposed to an adjacent anode oradjacent anodes via a solid electrolyte body.

According to the electrochemical cell of the present invention, it ispreferable that as viewed in a direction orthogonal to the flowchannels, every first gas flow channels excluding those in extremelyopposite sides of the honeycomb structural body is adjacent to foursecond gas flow channels, whereas every second gas flow channelsexcluding those in extremely opposite sides is adjacent to four firstgas flow channels.

The process for producing the electrochemical cell according to thepresent invention is characterized by including the steps of forming agreen molded body of said structural body by simultaneously extrusionmolding a body for said at least one electrolyte body and a body forsaid at least two interconnectors, obtaining the structural body byfiring said green molded body, and forming said anodes and cathodes onsaid respective walls defined by said part of at least one solidelectrolyte body and said part of at least two interconnectors andconstituting the respective first and second gas flow channels,respectively.

Another aspect of the process for producing the electrochemical cellaccording to the present invention is characterized by including thesteps of forming a green molded body of said structural body bysimultaneously extrusion molding a body for said at least oneelectrolyte body and a body for said at least two interconnectors,applying respective materials for said anodes and cathodes on saidrespective walls defined by said part of at least one solid electrolytebody and said part of at least two interconnectors and constituting therespective first and second gas flow channels, respectively, and firingthe green molded body together with the materials applied.

The present invention is also related to an electrochemical deviceprovided with the electrochemical cell or cells set forth above.

Having repeatedly made investigations to produce solid oxide fuel cellshaving a monolithic structure and a high electric power-generatingefficiency, the present inventors have reached the technical idea thatin order to produce such a solid oxide fuel cell, a honeycomb structuralbody is formed by integrating at least one dense solid electrolyte bodyand at least two dense interconnectors, and electrodes are formed onwalls of channels extending through the honeycomb structural body.

According to the thus constructed electrochemical cell, thepower-generating efficiency per unit volume is extremely high, andgas-tightness of the channels of the honeycomb structure areindependently assured by the dense solid electrolyte body and theinterconnectors, so that a power-generating device having a seal-lessstructure can be readily produced. In addition, the honeycomb-moldedbody to constitute at least one solid electrolyte body and at least twointerconnectors can be produced by simultaneous extrusion molding.Further, since the solid electrolyte body and the interconnector areboth required to be dense or gas-tight, it is easy to integrally sinterthem without necessitating fine control of their porosities to fall intheir respective specific ranges as in the case of the air electrode orfuel electrode.

Furthermore, since the interconnector and the solid electrolyte body areboth made of their respective dense materials with high relativedensities, the honeycomb structure body constituted by these densematerials has a high structural strength.

The air electrode and the fuel electrode may be formed by feedingrespective materials for the air electrode and the fuel electrode intothe channels of the honeycomb structural body formed above, attachingthe materials upon the respective walls of the channels, and sinteringthe attached materials.

The present inventors applied the above structure to electrochemicalcells other than the SOFC, for example, the steam electrolysis cell, andthey confirmed that the efficiency per unit volume, e.g., electrolysisefficiency can be also largely enhanced, and the above mentionedfunction and effects can be obtained.

These and other objects, features and advantages of the presentinvention will be apparent from the following description of theinvention when taken in conjunction with the attached drawings, with theunderstanding that any modifications, variations and changes may beeasily made by the skilled person in the art to which the inventionpertains.

BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS

For a better understanding of the invention, reference is made to theattached drawings, wherein:

FIG. 1 is a cross-sectional view illustrating a part of anelectrochemical cell 10A according to a first embodiment of the presentinvention;

FIG. 2 is a cross-sectional view illustrating a part of anelectrochemical cell 10B according to a second embodiment of the presentinvention;

FIG. 3 is a cross-sectional view illustrating a part of anelectrochemical cell 10C according to a third embodiment of the presentinvention;

FIG. 4 is a cross-sectional view illustrating a part of anelectrochemical cell 10D according to a fourth embodiment of the presentinvention;

FIG. 5 is a perspective view for illustrating the outer configuration ofone embodiment of the electrochemical cell according to the presentinvention;

FIG. 6 is a sectional view for diagrammatically illustrating a favorableembodiment of an electrochemical device to which an electrochemical cellaccording to the present invention is applied;

FIG. 7 is a sectional view for diagrammatically illustrating anotherfavorable embodiment of an electrochemical device to which anelectrochemical cell according to the present invention is applied;

FIG. 8 is a diagrammatic view for illustrating the extrusion moldingprocess for producing a structural body for an electrochemical cellaccording to the present invention;

FIGS. 9( a) through 9(h) diagrammatically illustrate the embodiment inFIG. 8;

FIGS. 10( a) through 10(d) diagrammatically illustrate an embodimentsimilar to FIG. 9( a) through FIG. 9( h); and

FIG. 11 diagrammatically illustrates a sectional view of the embodimentof FIG. 10( a) through FIG. 10( d).

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be explained in more detail with reference tomore specific embodiments to which the present invention should not belimited.

The entire configuration of the honeycomb structural body is notparticularly limited to any configuration. Further, the configuration ofeach channel in the honeycomb structural body is not limited to aparticular one. However, from the standpoint of effectively utilizingthe space, the cross-sectional shape of each channel is preferably ofsuch a shape as an isosceles triangular shape, an equilateral triangularshape, a rectangular shape, a square shape or an equilateral hexagonalshape that the sections of the channels may fill a plane at an end sidethereof. In addition, the channels may be designed such that thechannels having different cross-sectional shapes such as an equilateraltriangular shape and an equilateral hexagonal shape may be adjacent toeach other.

The material of the interconnector is preferably a perovskite-typecomplex oxide containing lanthanum, more preferably lanthanum chromite,because lanthanum chromite has heat resistance, oxidation resistance andreduction resistance.

The material of the solid electrolyte body is preferablyyttria-stabilized zirconia or yttria partially stabilized zirconia, butother materials may be also used. In the case of an NOx decompositioncell, cerium oxide is preferable, too.

A raw material for the anode and cathode is preferably a pervskite-typecomplex oxide containing lanthanum, more preferably lanthanum manganiteor lanthanum cobaltite, most preferably lanthanum manganite. Lanthanumchromite and lanthanum manganite may be doped with strontium, calcium,chromium (for lanthanum manganite), cobalt, iron, nickel or aluminum.Further, the raw material may be palladium, platinum, ruthenium, a mixedpowder of platinum and zirconia, a mixed powder of palladium andzirconia, a mixed powder of ruthenium and zirconia, a mixed powder ofplatinum and cerium oxide, a mixed powder of palladium and cerium oxide,or a mixed powder of ruthenium and cerium oxide.

The electrochemical cell according to the present invention may be usedas an oxygen pump to supply oxygen.

Further, the electrochemical cell according to the present invention maybe used as a high temperature steam electrolysis cell. This cell may bealso used as a device for producing hydrogen, or may be used as a devicefor removing steam. In this case, the following reactions occur atrespective electrodes.Cathode: H₂O+2e ⁻→H₂+O²⁻Anode: O²⁻→2e ⁻+½O₂

Furthermore, the electrochemical cell according to the present inventionmay be used as an NOx decomposing cell. This decomposing cell can beused as a purifier for exhaust gases from an automobile or an electricpower-generating apparatus. Although the exhaust gases from the gasolineengines are now disposed of with three-way catalysts, such three-waycatalysts will be less effective if the number of low mileage typeengines such as lean burn engines and diesel engines. That is, since thecontent of oxygen in exhaust gases from those engines is large, such athree-ay catalyst cannot well work with respect to low mirage typeengines.

If the electrochemical cell according to the present invention is usedas an NOx decomposing cell, it can remove oxygen in exhaust gasesthrough the solid electrolyte filmy body, and simultaneously decomposeNOx into N₂ and O²⁻ and remove the oxygen produced by thisdecomposition. Besides the above process, water vapor in the exhaustgases is electrolyzed into hydrogen and oxygen, and this hydrogenreduces NOx into N₂.

If the electrochemical cell is used as the NOx decomposing cell, thesolid electrolyte filmy body is particularly preferably made of a ceriumoxide based ceramic material, whereas the cathode material is preferablypalladium or palladium-cerium oxide cermet.

FIGS. 1 to 4 are cross sectional views all illustrating parts ofelectrochemical cells as preferred embodiments according to the presentinvention as cut in a direction crossing channels. In theelectrochemical cell 10A of FIG. 1, first gas (e.g. oxidative gas) flowchannels 6A and second gas (e.g., fuel gas) flow channels 7A all havingan almost square cross section are formed in a structural body 1A. Acathode 4A is formed on a surrounding wall surface of each first gasflow channel 6A, whereas an anode 5A is formed on that of each secondgas flow channel 7A. In FIG. 1, both the flow channels 6A and the flowchannels 7A are arranged vertically, while the gas flow channels 6A areopposed to the respectively adjacent gas flow channels 7A in a lateraldirection via a solid electrolyte body 3A.

The structural body 1A also includes an interconnectors 2A and the abovesolid electrolyte body 3A, and each of the flow channels 6A and 7A issurrounded in a half by a part of the interconnector 2A and in theremaining half by a part of the solid electrolyte body 3A. Consequently,each of the flow channels 6A and 7A is kept gas-tight in across-sectional direction thereof. In the electrochemical cell 10A ofFIG. 1, two pairs of the first gas flow channel 6A rows and the secondgas flow channels 7A rows are arranged in the honeycomb structural body1A, while the first gas flow channels 6A rows and the second gas flowchannel 7A rows are alternatively arranged in the lateral direction, andthe interconnectors 2A are arranged at opposite sides of the structuralbody 1A and between the two pair of the first gas flow channel 6A rowsand the second gas flow channels 7A rows.

In the electrochemical cell 10B of FIG. 2, first gas flow channels 6Band second gas flow channels 7B all having an almost squarecross-sectional shape are formed in a structural body 1B. A cathode 4Bis formed on a surrounding wall surface of each of the first gas flowchannel 6B, and an anode 5B is formed on that of each of the second gasflow channels 7B.

The first gas flow channels 6B and the second gas flow channels 7B arearranged alternatively as viewed vertically in FIG. 2. As to theadjacent two rows, the first and second gas flow channels 6B and 7B arestaggered in every other row vertically by a half of a side of each flowchannel as viewed in the lateral direction of FIG. 2. That is, one firstgas flow channel 6B and one second gas flow channel 7B in one row arehalf-by-half opposed to one flow channel 6B in an adjacent row.Accordingly, each first flow channel 6B is adjacent to four second flowchannels 7B, excluding those located at opposite sides of the structuralbody, whereas each second flow channel 7B is adjacent to four first flowchannels, excluding those located at opposite sides of the structuralbody. When the configuration in FIG. 2 is adopted, the area of theelectrodes can be increased, and efficiency of the electrochemical cell,for example, power-generating efficiency, electrolyzing efficiency, oroxygen-feeding efficiency can be enhanced. Further, in order to obtain agiven efficiency as referred to above, the entire electrochemical devicecan be made compact.

The structural body 1B also includes dense interconnectors 2B and densesolid electrolyte bodies 3B, and each of the flow channels 6B and 7B issurrounded in a portion by a part of the interconnector 2B and in theremaining portion by a part of the solid electrolyte body 3B.Consequently, each of the flow channels 6B and 7B is kept gas-tight in across-sectional direction thereof. In the electrochemical cell 10B ofFIG. 2, the first gas flow channel 6B zigzag lines and the second gasflow channels 7B zigzag lines are alternatively arranged in the verticaldirection, and the interconnectors 2A are arranged at opposite sides ofthe structural body 1A and between the two pair of the first gas flowchannel 6A lines and the second gas flow channels 7A lines.

In the electrochemical cell of FIG. 3, a structural body 10C includesdense interconnectors 2C and dense solid electrolyte bodies 3Cvertically alternatively piled one upon another, and a number ofchannels each having a triangular cross section are formed among theinterconnectors 2C and the solid electrolyte bodies 3C in the structuralbody 10C. A pair of a line of first gas flow channels 6C and a line ofsecond gas flow channels 7C are opposed to each other via each of thesolid electrolyte bodies 3C, and each of the first and second gas flowchannels 6C and 7C is surrounded by a part of the interconnector 2C anda part of the solid electrolyte body 3C as shown in FIG. 3. As viewedvertically, the lines of the first gas flow channels 6C and the lines ofthe second gas flow channels are alternatively arranged. A cathode 4C isformed on a surrounding wall surface of each first gas flow channels 6C,and an adnode 5C formed on that of each of the second gas flow channels7C. Electric power is to be generated between a pair of the adjacentfirst and second gas flow channels 6C and 7C opposed to each other viathe solid electrolyte body 3C. Between the adjacent first gas flowchannels 6C in each line and between the adjacent second flow channels7C in each line are formed channels 8 each having an almost triangularcross section. Each of the first and second gas flow channels 6C and 7Cis kept by the gas-tight interconnector 2C and the gas-tight solidelectrolyte body 3C as viewed in a crossing direction thereof.

In the electrochemical cell 10D of FIG. 4, a structural body 1D includesgas-tight interconnectors 2D and gas-tight solid electrolyte bodies 3Dlaterally alternatively piled one upon another and forming zigzag linesof first gas flow channels 6D and zigzag lines of second gas flowchannels 7D in which the former zigzag lines are opposed tocorresponding latter zigzag lines via the respective solid electrolytebodies 3D as shown. The first and second gas flow channels 6D and 7Deach have an almost equilateral hexagonal cross sectional shape, and arearranged in a honeycomb fashion. A cathode 4D is formed on a surroundingwall surface of each first gas flow channel 6D, and an anode 5D formedon that of each second gas flow channel 7D. Each of the first and secondgas flow channels 6D and 7D is surrounded and kept gas-tight as viewedin a crossing direction thereof by a part of the gas-tightinterconnector 2D and a part of the gas-tight solid electrolyte body 3D.

In the present invention, the channels in the honeycomb structural bodycan be easily shaped if the dimension of them in the cross section isnot less than 1 mm. Further, the dimension of the channel in the crosssection is preferably not more than 5 mm, because in this case, theelectric resistance of the electrochemical cell unit decreases and thearea of the electrodes per unit volume increases. From this point ofview, the dimension of each channel is more preferably not more than 3mm.

The entire shape of the honeycomb structural body is not limited to anyparticular one. However, as viewed diagrammatically three-dimensionallyin FIG. 5, a big capacity can be easily realized if the lateral andvertical dimensions “a” and “b” are not less than 5 cm, whereasexcessive increase in the pressure required for the extrusion moldingcan be prevented if the dimensions “a” and “b” are not more than 30 cm.If the longitudinal dimension “c” is less than 10 cm, the ratio of endportions not contributing to power generation, electrolysis or oxygenfeeding increases to deteriorate the efficiency of the electrochemicalcell. Therefore, the longitudinal dimension “c” is preferably not lessthan 10 cm. If the longitudinal dimension “c” is not more than 100 cm,handling is easy at the time of extrusion molding.

The entire shape of an electrochemical device using the electrochemicalcell according to the present invention is not limited to any particularone. In the electrochemical cell according to the present invention, theflow channels are each surrounded by a part of the gas-tightinterconnectors and a part of the gas-tight solid electrolyte body(bodies). Therefore, the electrochemical device preferably has aseal-less structure utilizing that of the electrochemical cell.Preferred embodiments of such seal-less structures are diagrammaticallyshown in FIGS. 6 and 7, respectively, in which interconnectors and solidelectrolyte bodies are omitted. In the electrochemical device of FIG. 6,a first gas and a second gas are flown in opposite directions,respectively. In the electrochemical device of FIG. 6, theelectrochemical cell 10A (10B, 10C, 10D) is placed in a can 13 of theelectrochemical device such that a gas chamber 15 and a gas chamber 16are defined at opposite sides of the can 13 as shown. An exhaust opening17 for the first gas and an exhaust opening 18 for the second gas areformed in the can 13.

The first gas flow channels 6A (6B, 6C, 6D) of the electrochemical cellare extended in a right direction of FIG. 6, and their extensions 11 areopened to a first gas feed mechanism (not shown) outside the can 13. Onthe other hand, the second gas flow channels 7A (7B, 7C, 7D) areextended in a left direction of FIG. 6, and their extensions 12 areopened to a second gas feed mechanism (not shown) outside the can 13.

The first gas is fed to the extensions 11 of the first gas flow channels6A as shown by arrows A, flown inside the flow channels 6A and furtherin the gas chamber 16 as shown by arrows B, and discharged through theexhaust opening 17. On the other hand, the second gas is fed to theextensions 12 of the second gas flow channels 7A as shown by arrows C,flown inside the flow channels 7A and further in the gas chamber 15 asshown by arrows D, and discharged through the exhaust opening 18.

In the electrochemical device of FIG. 7, the first gas and the secondgas are flown in the same direction. The electrochemical cell 10A (10B,10C, 10D) is placed in a can 13 such that a first gas chamber 30 and acombustion chamber 31 are defined at left and right sides of theelectrochemical cell inside the can 13, respectively. A first gas feedopening 19, a first gas exhaust opening 20, and a combustion gas exhaustopening 21 are formed in the can 13 as shown.

The second gas flow channels 7A (7B, 7C, 7D) of the electrochemical cellare extended in a left direction of FIG. 7, and their extensions 12 areopened to a second gas feed mechanism outside the can 13. None of thefirst gas flow channels 16 are extended outwardly from theelectrochemical cell.

The first gas is fed to the gas feed chamber 30 inside the can 13through the gas feed opening 19 as shown in an arrow E. Alternatively,the first gas may be fed to the gas chamber 30 from a direction verticalto the drawing paper, for example, from a front side of the drawingpaper. A part of the first gas is discharged outside through the exhaustopening 20, whereas the remainder is flown through the flow channels 6Aof the electrochemical cell as shown by arrows G, and discharged to thecombustion chamber 31 through downstream openings of the flow channels6A. On the other hand, the second gas is fed to the extensions 12 of thesecond gas flow channels 7A as shown by arrows F, flown through the flowchannels 7A and discharged into the combustion chamber 31. Thecombustion gas is flown as shown by arrows H, and discharged through theexhaust opening 21.

When the electrochemical device is used as an electric power-generatingdevice (SOFC), current collectors 14 are set at upper and lower endportions, respectively, in FIGS. 6 and 7. Electric power is takenoutside through these current collectors 14. A porous conductor having abuffering function, for example, a felt, is preferably set between eachcurrent collector and the SOFC, because stress is mitigated and contactelectric resistance is reduced in this case. Nickel is preferred as amaterial for the felt and the current collectors.

A preferred embodiment of the process for producing the electrochemicalcell according to the present invention will be explained with referenceto a diagrammatic view of FIG. 8. In this embodiment, a bodyconstituting a green molded body for the formation of theinterconnectors and a body constituting a green molded body for theformation of the solid electrolyte bodies are continuously fed into asingle die device so that the green molded bodies of the interconnectorsand the solid electrolyte bodies may be extruded through the die devicein a integrally joined fashion. Then, the extruded body is integrallysintered.

In a particularly preferred embodiment, the body constituting the greenmolded body for the formation of the interconnectors and the bodyconstituting the green molded body of the solid electrolyte bodies arecontinuously fed into a single die device such that the bodyconstituting the green molded body for the formation of theinterconnectors is pushed toward the die device through a firstextruding mechanism, whereas the body constituting the green molded bodyfor the formation of the solid electrolyte bodies is pushed toward thedie device through a second extruding mechanism. By so doing, the firstextruding mechanism and the second extruding mechanism can bemechanically adjusted with respect to the extruding speed and theextruding pressure so that peeling or curving of the extruded body maybe prevented.

The green molded body of each of the interconnector and the solidelectrolyte body is preferably made by molding a mixture in which anorganic binder and water are mixed into a main ingredient. As theorganic binder, polyvinyl alcohol, methyl cellulose, ethyl cellulose orthe like may be used. The addition amount of the organic binder ispreferably 0.5 to 5 parts by weight, if the weight of the mainingredient is taken as 10 parts by weight.

In the embodiment of FIG. 8, a green shaped body 25 for the formation ofthe interconnectors and a green shaped body 26 for the formation of thesolid electrolyte bodies are used. Each of the green molded bodies has,for example, a cylindrical shape. The die device 27 includes moldingbarrels 24A and 24B, a first die portion 27 a and a second die portion27 b communicating with the molding barrels 24A and 24B, respectively,plungers 23A and 23B slidably arranged inside the molding barrels 24Aand 24B, respectively, and not shown dies arranged in the die portions27 a and 27 b, respectively. The green molded body 25 for the formationof the interconnectors is placed in the molding barrel 24A, and thegreen molded body 26 for the formation of the solid electrolyte bodiesplaced in the molding barrel 24B.

The body 25 is pushed into the die portion 27 a by moving a shaft of theplunger 23A toward the die portion 27 a, whereas the body 26 is pushedinto the die portion 27 b by moving a shaft of the plunger 23B towardthe die portion 27 b. The bodies are molded in the form of theinterconnectors and the solid electrolyte bodies having thecross-sectional configuration as shown in FIG. 1, 2, 3 or 4. A referencenumeral 28 denotes a honeycomb structural body-extruding die. The thusextruded body may be fired at a firing temperature of 1400° C. to 1700°C. A reference numeral 28 is a honeycomb structural body-extruding die.

FIGS. 9( a) to 9(f) diagrammatically illustrating the embodiment shownin FIG. 8. The molding from FIG. 9( a) to FIG. 9( c) is effected by thedie device 27, whereas the molding from FIG. 9( c) to FIG. 9( e) iseffected by the honeycomb structural body-extruding die 28. FIGS. 9( a)to 9(e) are sectional views taken along lines IXa, IXb, IXc, IXd andIXe, respectively. Each of the green shaped bodies 25 and 26 (FIG. 9(a)) is extruded into plural planar bodies 29, 30 (FIG. 9( b)). Theplanar bodies 29 are inserted between the planar bodies 30 at an inletof the honeycomb-shaped body extruding die 28 as shown in FIG. 9( c).Then, each of the planar bodies 29 and 30 arrayed as in FIG. 9( c) isdivided into a row of rod-shaped bodies 29A and 30A in a matrix as shownin FIG. 9( d), and these rows of the rod-shaped bodies 29A and 30A areconverted into a honeycomb structural body 31 shown in FIG. 9( e). FIG.9( f) is an enlarged view of FIG. 9( c), FIG. 9( g) is an enlarged viewof FIG. 10( d), and FIG. 9( h) an enlarged view of FIG. 9( e) through adie not shown.

FIGS. 10( a) to 10(f) diagrammatically illustrate another embodimentsimilar to that shown in FIG. 8 and FIGS. 9( a) to 9(h). FIGS. 10( a) to10(d) are sectional views taken along lines IXa, IXb, IXc and IXd ofFIG. 11, respectively. The embodiment in FIGS. 10( a) to 10(d) differsfrom that in FIGS. 8 and 9( a) to 9(h) in that the steps in FIGS. 9( b)and 9(c) are modified. That is, each of the green shaped bodies 25 and26 (FIG. 9( a)) is extruded into plural rod-shaped bodies 31, 32 (FIG.10( b)), and the rod-shaped bodies 31 are inserted between therod-shaped bodies 32 at an inlet of the honeycomb-shaped body extrudingdie 28 as shown in FIG. 10( c). The thus arrayed rod-shaped bodies 31and 32 are molded into a honeycomb structural body shown in FIG. 10( d).In the embodiment of FIGS. 10( a) to 10(f) and FIG. 11, the die device27 may be integrally formed with the honeycomb structural body-extrudingdie 28.

Then, an anode material or a cathode material is applied to asurrounding wall surface of each of the channels through the thussintered body. Although this applying method is not limited to anyparticular one, according to a preferred embodiment, slurries of theanode material and the cathode material are poured into the respectivelyintended channels, and discharged therethrough, followed by drying.Thereby, their powdery materials are attached to the respectivelyintended channels. Then, the resulting honeycomb structural body isentirely fired at 1100° C. to 1500° C. to form anodes and cathodes.

The present inventors actually produced steam electrolysis cells asshown in FIGS. 1 to 4. Their honeycomb structural bodies composed of thesolid electrolyte bodies and the interconnectors were prepared asmentioned above. The steam electrolysis cells were produced by applyinga platinum paste to this honeycomb structural body.

More specifically, a slurry having fluidity was obtained by addingpolyethylene glycol into a commercially available platinum paste. Thisslurry was poured into every channel, thereby attaching the slurry ontothe wall surfaces thereof. In this case, since the anode and the cathodemay be made of the same material, it is unnecessary to pour differentmaterials for the anodes and the cathodes into respective channels as inthe case of SOFC.

Since any platinum slurry attached to a place other than the surroundingwall surfaces of the channels may cause short circuit, such a slurrymust be swept off. The thus obtained honeycomb structural bodies werefired, for example, at 1000° C. for 1 hour, thereby forming platinumanodes and cathodes.

With respect to the thus produced steam electrolysis cells, argon andargon containing steam were flown on the anode side and the cathodeside, respectively in the state that the cells were heated to 1000° C.,while current was flown between the anodes and the cathodes. Thereby,hydrogen could be generated.

Anodes and cathodes may be formed through immersing the structural bodyinto a slurry of a metal. For example, the structural bodies 1A, 1B, 1Cand 1D as explained above were prepared. A fluidic slurry was obtainedby adding polyethylene glycol into a commercially available platinumpaste. Each of the structural bodies was immersed into this slurry.

At that time, the platinum slurry was attached to not only surroundingwall surfaces of the channels but also end faces of the structural body.If the structural bodies with the slurry thus attached are fired, theanodes and the cathodes may be shorted. For this reason, portions nearthe respective end faces of the structural body were removed by cutting.By so doing, unnecessary platinum slurry can be easily removed from thestructural body without sweeping away it. The thus obtained honeycombbodies were fired at 1000° C., thereby forming the anodes and thecathodes made of platinum.

With respect to the thus produced steam electrolysis cells, argon andargon containing steam were flown on the anode side and the cathodeside, respectively, in the state that the cells were heated to 1000° C.,while current was flown between the anodes and the cathodes. Thereby,hydrogen could be generated.

As having been explained above, according to the present invention, theelectrochemical cells which each have a large area of the electrodes perunit voltage and high power-generating efficiency, high electrolysisefficiency, high oxygen generating efficiency or the like can beprovided. Further, the electrochemical cells are structurally relativelysimple, and need no special sealing mechanism and can be produced bysimultaneous sintering due to their structure.

1. An electrochemical cell comprising: at least one dense solidelectrolyte body of solid electrolyte material; at least two denseinterconnectors of interconnector material for conducting current; andcathodes and anodes, wherein said dense solid electrolyte body and denseinterconnectors are united as a structural body through which aplurality of first gas flow channels and a plurality of second gas flowchannels both extend in a given direction, each said gas flow channel isdefined and surrounded by planar walls, said planar walls being formedin part by said solid electrolyte material and in part by saidinterconnector material, said anodes are formed on said planar wallsdefining said first gas flow channels, said cathodes are formed on saidplanar walls defining said second flow gas channels, every anode isopposed to an adjacent cathode or adjacent cathodes through said solidelectrolyte material, and every cathode is opposed to an adjacent anodeor adjacent anodes through said solid electrolyte material, wherein saiddense solid electrolyte body and said interconnectors join at twolocations surrounding each gas flow channel, and each location isbetween adjacent corners of each gas flow channel.
 2. Theelectrochemical cell of claim 1, wherein as viewed in a directionorthogonal to the flow channels, every first gas flow channel excludingthose in extremely opposite sides of the structural body is adjacent tofour second gas flow channels, and wherein every second gas flow channelexcluding those in said extremely opposite sides is adjacent to fourfirst gas flow channels.
 3. The electrochemical cell of claim 1, whereina cross sectional view of each of the first and second gas flow channelsis one selected from the group consisting of an isosceles triangleshape, an equilateral triangular shape, a rectangular shape, a squareshape, and an equilateral hexagonal shape.
 4. An electrochemical deviceincluding an electrochemical cell, the electrochemical cell comprising:at least one dense solid electrolyte body of solid electrolyte material;at least two dense interconnectors of interconnector material forconducting current; and cathodes and anodes, wherein said dense solidelectrolyte body and dense interconnectors are united as a structuralbody through which a plurality of first gas flow channels and aplurality of second gas flow channels both extend in a given direction,each said gas flow channel is defined and surrounded by planar walls,two of said planar walls being formed in part by said solid electrolytematerial and in part by said interconnector material, said anodes areformed on said planar walls defining said first gas flow channels, saidcathodes are formed on said planar walls defining said second gas flowchannels, every anode is opposed to an adjacent cathode or adjacentcathodes through said solid electrolyte material, and every cathode isopposed to an adjacent anode or adjacent anodes through said solidelectrolyte material, said solid electrolyte body and saidinterconnectors join at two locations surrounding each gas flow channel,and each location is between adjacent corners of each gas flow channel.5. The electrochemical cell of claim 1, wherein at least one of said twoplanar walls comprises both the solid electrolyte material and theinterconnector material.
 6. The electrochemical cell of claim 4, whereinat least one of said two planar walls comprises both the solidelectrolyte material and the interconnector material.
 7. Theelectrochemical cell of claim 1, wherein at least one of said two planarwalls comprises half solid electrolyte material and half interconnectormaterial.
 8. The electrochemical cell of claim 4, wherein at least oneof said two planar walls comprises half solid electrolyte material andhalf interconnector material.